Configuration option for thread-stack protection.

[Sebastian Huber]

On 06/08/2020 14:12, Utkarsh Rai wrote:

> Hello,
> The thread-stack protection needs to be configured by the user. Two of 
> the options that need configuring during build time are -
> > Enabling thread stack protection ( THREAD_STACK_PROTECTION )- This 
> is a high-level option similar to RTEMS_SMP, RTEMS_POSIX_API  etc.
> > Size of the MMU pages - This is a BSP specific option.
>  Using the new build system we can configure these by adding BSP 
> option ( for eg. realview BSP has 'optmmusmallpages.yml'  for 4K mmu 
> pages). Similarly, we can have 'optthreadstackprotection.yml' similar 
> to 'optsmp.yml' for enabling thread stack protection.  Is there 
> something else we need to do, for specifying these options?
>
> Another option that needs to be specified is the number of thread 
> stacks that can be shared with a particular thread. This can be done 
> by specifying this in rtems/confdefs.h and then configured by the 
> application. I would request your opinion on this and whether this is 
> the right manner to proceed.

Yes, we probably need a new CPU option RTEMS_THREAD_STACK_PROTECTION or 
similar.

Why can't you use this option in the BSP to enable the 4KiB pages MMU?

With respect to the application configuration, we should consider to use 
thread-local storage for this. TLS is well supported on ARM, SPARC, 
PowerPC, RISC-V, and m68k.